Oxidation of 2-methylnaphthalene with ozone

Article abstract of DOI:10.1007/s11178-005-0098-x

In the oxidation of 2-methylnaphthalene with ozone in acetic acid, the oxidant reacts mainly at the double bonds of the substituted aromatic ring to give peroxy compounds. In the presence of cobalt diacetate and sodium bromide, oxidation of the 2-methyl g

Full text of DOI:10.1007/s11178-005-0098-x

Russian Journal of Organic Chemistry, Vol. 40, No. 12, 2004, pp. 1779–1781. Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 12, 2004,
pp. 1829–1830.
Original Russian Text Copyright © 2004 by Mamchur, Galstyan.
Oxidation of 2-Methylnaphthalene with Ozone
A. V. Mamchur and G. A. Galstyan
Rubezhnoe Division, Dal’East-Ukrainian National University,
ul. Lenina, 31, Rubezhnoe, Lugansk oblast, 93000 Ukraine
Received October 29, 2003
Abstract—In the oxidation of 2-methylnaphthalene with ozone in acetic acid, the oxidant reacts mainly at the
double bonds of the substituted aromatic ring to give peroxy compounds. In the presence of cobalt diacetate
and sodium bromide, oxidation of the 2-methyl group occurs with formation of 2-naphthoic acid. The major
product in the oxidation of 2-methylnaphthalene with ozonated transition metal compounds is 2-methyl-1,4-
naphthoquinone.
The reaction of ozone with 2-methylnaphthalene (I)
attracts interest from the viewpoint of development of
selective procedures for the synthesis of 2-naphthoic
acid (II) and 2-methyl-1,4-naphthoquinone (III).
However, published data on this reaction are few in
number: In 1957, Bailey and Garsia-Sharp [1] showed
that ozonation of 2-methylnaphthalene (I) occurs at
the methyl-substituted ring with rupture of the
aromatic system.
We have found that the reaction of 2-methylnaph-
thalene (I) with ozone, depending on the conditions,
may result not only in rupture of the aromatic system
but also in formation of 2-naphthoic acid (II) or
quinone (III). The major products of the oxidation of
I in acetic acid are hydroperoxides IV (84%); also,
unidentified tarry compounds and small amounts of
acid II (2%) and quinone III (1.5%) are formed. The
reaction follows the first-order kinetics with respect to
the reactants, in keeping with the radical ion mech-
anism. The oxidation of 1 mol of I requires 1.86 mol
of ozone [2]. Hydroperoxides IV are stable to the
action of ozone; they react with potassium iodide with
liberation of iodine in an amount equivalent to two
hydroperoxy groups per molecule.
The above stated is consistent with the modern
views on the mechanism of ozonation of aromatic
Scheme 1.
O–
O
O
H
O3
Me
O3
Me
Me
I
A
B
O
O
(OOH)2
Me
O
a
Me
· · ·
H2
V
IV
O
·
H
O
Me
Me
b
·
· · ·
–O2
O
C
III
1070-4280/04/4012-1779 © 2004 MAIK “Nauka/Interperiodica”

MAMCHUR, GALSTYAN
1780
Scheme 2.
OH
OH
OH
Me
Me
O–
Me
·
O3
C
+
–O2
O
·
O
H
O
H
O–
OH
OH
HO
O
O
Me
Me
O3
III
–H2O, –O2
OH
compounds [3, 4]. In the first stage, ozone reacts with
the substituted aromatic ring in I to give π-complex A;
charge transfer in the latter leads to formation of
σ-complex B whose further transformations can follow
two pathways. The first pathway (a) leads to ozonide
V and then to hydroperoxides IV. According to path-
way b, dissociation of the O–O bond in B gives
structure C which is then converted into quinone III
(Scheme 1). Presumably, the transformation of V into
hydroperoxides IV follows the scheme proposed in [1]
for the ozonation of I in aqueous methanol .
The mechanism of formation of naphthoquinones
was not described previously; it is now in the develop-
ment stage. Quinone III is presumed to be formed
according to the scheme proposed in [5] for the oxida-
tion of anthracene to anthraquinone (Scheme 2).
The above data show that, under conditions of non-
catalytic and catalytic ozonation, the main products in
the oxidation of arene I may be either hydroperoxides
IV or napththoic acid II. Quinone III cannot be ob-
tained by these reactions. We previously [9] proposed
a procedure for the synthesis of quinone III, which
involves initial ozonation of a mixture of Cr(III) and
Mn(II) salts according to Scheme 5.
Scheme 5.
·
Mn(II)
+
O3
+
+
H+
Mn(III)
Cr(VI)
+
HO
+
O2
·
Cr(III)
3Mn(III)
+
3Mn(II)
In the second step, 2-methylnaphthalene (I) is ox-
idized with the resulting ozonated chromium(VI) and
manganese(III) compounds. 2-Methyl-1,4-napththo-
quinone (III) is thus obtained in 70% yield.
Scheme 3 [6] illustrates the formation of 2-naph-
thoic acid (II).
EXPERIMENTAL
Scheme 3.
·
·
ArCH3
+
O3
ArCH2
+
HO
+
O2
The ozonation process was studied in a catalytic
reactor maintained at a constant temperature. The reac-
tion was carried out in the kinetic mode (the reactor
was shaken at a frequency of 7 s–1) [10]. The concen-
trations of 2-methylnaphthalene (I) and 2-methyl-1,4-
naphthoquinone (III) were determined by gas–liquid
chromatography on an LKhM-80 instrument equipped
with a flame ionization detector and a 2-m column
packed with 5 wt % of PNFS-6 on Chromaton N-AW;
injector temperature 250°C, oven temperature 160°C.
The concentration of hydroperoxides IV was deter-
mined by iodometric titration, and naphthoic acid II
was quantitated by potentiometric titration in acetone.
·
·
ArCH2
+
O2
ArCH2O2
Products
·
2ArCH2O2
The selectivity of oxidation of the methyl group
increases in the presence of cobalt bromide catalyst. At
373 K and a catalyst concentration of 0.015 M, the
yield of acid II rises from 2 to 90%. In this case, no
destructive oxidation of the aromatic system occurs
since ozone reacts with the reduced form of the cata-
lyst, Co(II)Br–. The reactive catalytic species Co(II)Br·
is then reduced via oxidation of the methyl group in
the substrate [7, 8] (Scheme 4).
REFERENCES
Scheme 4.
Co(II)Br–
ArCH3
+
O3
Co(II)Br
+
H+
Co(II)Br
+
HO
+
+
O2
H+
·
·
1. Bailey, P.S. and Garsia-Sharp, F.Y., J. Org. Chem., 1957,
·
·
+
ArCH2
+
Co(II)Br–
vol. 22, p. 1008.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 12 2004

OXIDATION OF 2-METHYLNAPHTHALENE WITH OZONE
1781
2. Mamchur, A.V., Galstyan, G.A., and Potapenko, E.V.,
Neftekhimiya, 2002, vol. 42, p. 287.
with Organic Compounds), Moscow: Nauka, 1974,
p. 181.
3. Pryor, W.A., Gleicher, G.J., and Church, D.F., J. Org.
Chem., 1983, vol. 48, p. 4198.
7. Galstyan, G.A., Galstyan, T.M., and Mikulenko, L.I.,
Kinet. Katal., 1994, vol. 35, p. 255.
4. Avzyanova, E.V., Kabal’kova, N.N., and Sheresho-
vets, V.V., Izv. Ross. Akad. Nauk, Ser. Khim., 1996,
p. 371.
8. Galstyan, A.G., Tyupalo, N.F., and Andreev, A.Yu.,
Kinet. Katal., 2003, vol. 44, p. 91.
9. Galstyan, T.M., Mamchur, A.V., Galstyan, G.A., and
Potapenko, E.V., Zh. Prikl. Khim., 2000, vol. 73, p. 660.
5. Bailey, P.S., Chem. Rev., 1958, vol. 58, p. 962.
10. Galstyan, G.A., Galstyan, T.M., and Sokolova, S.M.,
6. Razumovskii, S.D. and Zaikov, G.E., Ozon i ego reaktsii
s organicheskimi soedineniyami (Ozone and Its Reactions
Kinet. Katal., 1992, vol. 33, p. 779.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 12 2004